The entire game is built on it. If you dislike RNG, I would suggest a new game.
Heck, I would suggest a new genre. ARPG's are all built on RNG.

It's what keeps you farming loot, even after you've already got loot.

That all said, I think everything hinges on one point exactly;

What does corruption do?
Everything is nice, but everything also hinges on this fact ;)

Agreed but if it turns your gear into shit it's fucking gay and needs to be removed.

If there was a chance that your gear would become worse, but also a chance that the gear would become better... well then that's the sort of RNG I like - Add to this a possible way to remove corruption when it has a negative effect and we have some interesting options.